Plate tectonics

Description

Natural processes which cause earthquakes and volcanoes including detail on constructive, conservative and destructive (subduction and collision zones) margins, hotspots, fault lines and some information on volcano types
Jess Molyneux
Flashcards by Jess Molyneux, updated more than 1 year ago
Jess Molyneux
Created by Jess Molyneux about 9 years ago
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Resource summary

Question Answer
Name the 8 major tectonic plates. Eurasian African Australian Pacific Indian Antarctic North American South American
What causes the movement of tectonic plates? (Hint: where is this?) Convection currents in the mantle beneath the crust
Name the two different types of plate. Continental Oceanic
What type of rock are continental plates made up of? (Bonus: give some properties) Granite Low density igneous rock 2.87g per cubic cm
What type of rock are oceanic plates made up of? (Bonus: give some properties) Basalt High density igneous rock 3.14g per cubic cm
What name is given to plate margins where the plates are moving apart? Constructive or divergent
Give an example of a constructive plate margin. (Hint: where is it found? Which plates are involved? How long is it? How quickly is it forming?) Mid Atlantic Ridge North American and Eurasian plates Moving apart at around 3cm per year 12 000 miles long Centre of Atlantic ocean
What 3 changes would be observed at a constructive plate margin? Plates move apart - fissures or rift valleys Magma rises to the surface - new crust Central mountains form
What 3 hazards are associated with a constructive plate margin? Fissure volcanoes OR volcanic islands Earthquakes along transform faults
What are transform faults? (Bonus: why do earthquakes tend to occur along them? Joins between different types or ages of bands of rock They are the weakest point so pressure builds there
What name is given to plate margins where the plates are sliding past one another? Conservative or transform
Give an example of a conservative plate margin. (Hint: where is it found? Which plates are involved? What are the consequences?) San Andreas Fault California Pacific and North American plates 5 large earthquakes from 1906 - 1994
What changes would be observed at a conservative plate margin? No special surface features Sliding motion causes plates to stick or lock - pressure builds up - a sudden movement releases this tension and sends shockwaves
What hazard is associated with a conservative plate margin? Earthquakes
What name is given to plate margins where the plates are moving towards one another? Destructive or convergent
What are the two types of destructive margin? (Bonus: distinguish between them) Subduction zone (continental, oceanic OR oceanic, oceanic) Collision zone (continental, continental)
Why does subduction occur when at least one of the plates is oceanic? Oceanic plates are made up of basalt which is of a higher density (than granite) and so sinks
Give an example of a subduction zone. (Hint: which plates are involved? What 3 changes have occurred?) Nazca and South American plates Formed part of the Andes String of volcanoes along mountain crest Deep trench in Pacific ocean
What 3 changes would be observed at a subduction zone? (Hint: consider both plates) Continental plate forces oceanic into mantle (subduction) where it melts along with water and sea deposits Fold mountains are along edge of continental plate Oceanic trench formed
What 2 hazards are associated with a subduction zone? (Bonus: and why?) Earthquakes (intensive folding of the rock leads to slipping and breaking rock) Composite volcanoes (melted rock rises through continental plate - volcanic eruptions at surface, when the oceanic plate melts, gas is formed - explosive volcano)
Why does subduction NOT occur between two continental plates? (Bonus: what does this mean for activity in these places?) Both plates are too buoyant There is no volcanic activity - no new magma created
Give two examples of collision zones. (Hint: which plates are involved? what changes have occurred?) Eurasian and African plates - the Alps Indo-Australian and Eurasian - the Himalayas
What change would be observed at a collision zone? Pressure as plates move towards one another causes leading edge of both plates to buckle on collision - fold mountains created
What hazard is associated with a collision zone? (Bonus: and why?) Earthquakes (locking or sticking may occur and cause pressure to build)
What characterises a fissure volcano? (Hint: there are 2 features) Runny lava / lava fountains Long, flat vent
Where are fissure volcanoes usually found or formed? Constructive plate margins
What characterises a composite volcano? (Hint: there are 3 features) Thick, viscous lava Tall cone shape Explosive eruptions (due to pressure from sticky lava)
Where are composite volcanoes usually found or formed? Subduction zones
What characterises a shield volcano? (Hint: there are 2 features) Low cone, gentle slope Runny lava
What are hotspots? Small areas of the Earth's crust where unusually high heat flow is associated with volcanic activity
Explain the presence of extinct volcanoes close to hotspots. A plume of heat directly from the core created the volcano. Plate movement caused it to move off the hotspot so no longer had a supply of magma.
Give an example of a hotspot which has created a string of volcanic islands. (Bonus: how long is it?) Hawaii String of volcanic islands 3,700 miles long
What may cause an earthquake in an area distant from a plate boundary? (Hint: there are 3 things) Fault lines Rising land (previously crushed by glaciers) Historic plate collision - lines of weakness
Why is the San Andreas Fault particularly prone to earthquakes? Not a single fracture Line of interrelated faults 'Domino effect' when tension released
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